Expandable sheath

ABSTRACT

A delivery sheath includes an outer tubular layer and an initially folded inner tubular layer. When an implant passes therethrough, the outer tubular layer expands and the inner tubular layer unfolds into an expanded lumen diameter. The sheath may also include selectively placed longitudinal support rods that mediate friction between the inner and outer tubular layers to facilitate easy expansion, thereby reducing the push force needed to advance the implant through the sheath&#39;s lumen.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/880,109, filed Oct. 9, 2015 and entitled EXPANDABLE SHEATH, whichclaims the benefit of U.S. Provisional Patent Application Ser. No.62/145,968 filed on Apr. 10, 2015 and entitled EXPANDABLE DELIVERYSHEATH. This application is also a continuation of U.S. application Ser.No. 14/880,111, filed Oct. 9, 2015 and entitled EXPANDABLE SHEATH WITHELASTOMERIC CROSS SECTIONAL PORTIONS, which claims the benefit of U.S.Provisional Patent Application Ser. No. 62/145,968, filed Apr. 10, 2015and entitled EXPANDABLE DELIVERY SHEATH. All of the aforementionedapplications are hereby incorporated by reference herein in theirentireties and for all purposes.

FIELD

The present application concerns embodiments of a sheath for use withcatheter-based technologies for repairing and/or replacing heart valves,as well as for delivering an implant, such as a prosthetic valve to aheart via the patient's vasculature.

BACKGROUND

Endovascular delivery catheter assemblies are used to implant prostheticdevices, such as a prosthetic valve, at locations inside the body thatare not readily accessible by surgery or where access without invasivesurgery is desirable. For example, aortic, mitral, tricuspid, and/orpulmonary prosthetic valves can be delivered to a treatment site usingminimally invasive surgical techniques.

An introducer sheath can be used to safely introduce a deliveryapparatus into a patient's vasculature (e.g., the femoral artery). Anintroducer sheath generally has an elongated sleeve that is insertedinto the vasculature and a housing that contains one or more sealingvalves that allow a delivery apparatus to be placed in fluidcommunication with the vasculature with minimal blood loss. Aconventional introducer sheath typically requires a tubular loader to beinserted through the seals in the housing to provide an unobstructedpath through the housing for a valve mounted on a balloon catheter. Aconventional loader extends from the proximal end of the introducersheath, and therefore decreases the available working length of thedelivery apparatus that can be inserted through the sheath and into thebody.

Conventional methods of accessing a vessel, such as a femoral artery,prior to introducing the delivery system include dilating the vesselusing multiple dilators or sheaths that progressively increase indiameter. This repeated insertion and vessel dilation can increase theamount of time the procedure takes, as well as the risk of damage to thevessel.

Radially expanding intravascular sheaths have been disclosed. Suchsheaths tend to have complex mechanisms, such as ratcheting mechanismsthat maintain the shaft or sheath in an expanded configuration once adevice with a larger diameter than the sheath's original diameter isintroduced.

However, delivery and/or removal of prosthetic devices and othermaterial to or from a patient still poses a risk to the patient.Furthermore, accessing the vessel remains a challenge due to therelatively large profile of the delivery system that can causelongitudinal and radial tearing of the vessel during insertion. Thedelivery system can additionally dislodge calcified plaque within thevessels, posing an additional risk of clots caused by the dislodgedplaque.

U.S. Pat. No. 8,790,387, which is entitled EXPANDABLE SHEATH FORINTRODUCING AN ENDOVASCULAR DELIVERY DEVICE INTO A BODY and isincorporated herein by reference, discloses a sheath with a split outerpolymeric tubular layer and an inner polymeric layer, for example inFIGS. 27A and 28. A portion of the inner polymeric layer extends througha gap created by the cut and can be compressed between the portions ofthe outer polymeric tubular layer. Upon expansion of the sheath,portions of the outer polymeric tubular layer have separated from oneanother, and the inner polymeric layer is expanded to a substantiallycylindrical tube. Advantageously, the sheath disclosed in the '387patent can temporarily expand for passage of implantable devices andthen return to its starting diameter.

Despite the disclosure of the '387 patent, there remains a need forfurther improvements in introducer sheaths for endovascular systems usedfor implanting valves and other prosthetic devices.

SUMMARY

The needs above and other advantages are provided by an expandableintroducer sheath for a delivery of an implant mounted on a catheter.The sheath includes an elastic outer tubular layer and an inner tubularlayer having a thick wall portion integrally connected to a thin wallportion. The inner tubular layer can have a compressed condition/foldedconfiguration wherein the thin wall portion folds onto an outer surfaceof the thick wall portion under urging of the elastic outer tubularlayer. When the implant passes therethrough, the outer tubular layerstretches and the inner tubular layer at least partially unfolds into anexpanded lumen diameter to accommodate the diameter of the implant. Oncethe implant passes, the outer tubular layer again urges the innertubular layer into the folded configuration with the sheath reassumingits smaller profile. In addition to a reduced initial profile size, theintegral construction of the inner tubular layer guards against theleaks and snags of prior art split-tube and uniform thickness linercombinations. The sheath may also include selectively placedlongitudinal rods that mediate friction between the inner and outertubular layers to facilitate easy expansion and collapse, therebyreducing the push force needed to advance the oversized implant throughthe sheath's lumen.

Embodiments include a sheath for delivery of an implant mounted on acatheter. The sheath may include an elastic outer tubular layer and aninner tubular layer. The outer tubular layer defines an initial elasticlumen extending axially therethrough and having an initial diameter. Theinner tubular layer has a thick wall portion integrally connected to athin wall portion—such as by co-extrusion during manufacture. The thickwall portion has a C-shaped cross section with a first longitudinallyextending end and a second longitudinally extending end. The thin wallportion extends between the first and second longitudinally extendingends to define an expanded lumen extending axially through the innertubular layer. The expanded lumen has an expanded diameter larger thanthe initial diameter of the initial elastic lumen. The inner tubularlayer, in a compressed condition, extends through the initial elasticlumen of the elastic outer tubular layer with the elastic outer tubularlayer urging the first longitudinally extending end under the secondlongitudinally extending end of the inner tubular layer. The innertubular layer in a locally expanded condition has the first and secondlongitudinally extending ends radially expanded apart, against theurging of the elastic outer tubular layer by passage of the implant,into a non-overlapping condition with the thin wall portion extendingtherebetween to form the expanded lumen. The inner tubular layer isconfigured to be urged by the outer elastic tubular layer into thecompressed condition after passage of the implant through the expandedlumen.

In another aspect, the outer surface of the inner tubular layer and/orthe inner surface of the outer tubular layer can have a lubriciouscoating configured to allow free relative sliding of the outer elasticlayer and inner tubular layer. A longitudinally extending portion orstrip of the outer surface of the inner tubular layer can be adhered toa corresponding longitudinally extending portion of the inner surface ofthe outer tubular layer to provide some restriction on rotation betweenthe inner and outer layer.

In another embodiment, the tubular layers may include a plurality oflongitudinal rods coupled to their surfaces. For example, the innersurface of the outer tubular layer may include rods extending into theinitial elastic lumen. The rods are configured to provide a bearingsurface to facilitate relative movement of the layers when moving fromthe locally expanded condition to the compressed condition (and back).Longitudinal rods embedded within the elastic outer tubular layer canalso protrude from both an inner and outer surface of the elastic outertubular layer.

The longitudinal rods may be circumferentially spaced about the innersurface of the outer tubular layer. The inner tubular layer may alsoinclude contact-area reducing rods coupled to its inner surface.

In another aspect, the sheath can include a radiopaque tubular layerextending around a longitudinal portion of the elastic outer tubularlayer. In some embodiments, the outer tubular layer is comprised of atransparent material

In some embodiments, a heat-shrink tube can be applied around theelastic outer tubular layer at a distal end of the elastic outer tubularlayer.

In some embodiments, a distal portion of the elastic outer tubular layerand inner tubular layer are adhered to each other. For example, a distalportion of the elastic outer tubular layer can be adhered to an expandedouter surface of the inner tubular layer. The distal portion of theelastic outer tubular layer and inner tubular layer can be reflowed ontoeach other into a sealed configuration. In some implementations, adistal portion of the sheath has a flared shape. The flared shape can befolded into an overlapping arrangement.

A method of using the expandable introducer sheath can include insertingthe sheath, at least partially, into the blood vessel of the patient. Animplant is advanced through the inner tubular layer of the sheath. Theinner tubular layer transitions from a compressed condition to a locallyexpanded condition using the outwardly directed radial force of theimplant. After passage of the implant, the locally expanded innertubular layer is contracted at least partially back to the compressedcondition by the inwardly directed radial force of the outer elastictubular layer. During the local expansion of the inner tubular layer,the first and second longitudinally extending ends move towards and thenaway from each other. During contraction of the locally expanded innertubular layer, the first and second longitudinally extending ends movetoward and then away from each other to return, at least partially, tothe compressed condition.

DESCRIPTION OF DRAWINGS

FIG. 1 is an elevation view of an expandable sheath along with anendovascular delivery apparatus for implanting a prosthetic implant.

FIG. 2 is a cross sectional view of a sheath and a hub.

FIG. 3A is a magnified view of distal tip of the sheath.

FIG. 3B is a cross sectional view of the distal tip of the sheath, takenalong line 3B-3B of FIG. 3A.

FIG. 4 is a cross sectional view of an exemplary implementation of theouter tubular layer of the sheath.

FIG. 5 is a cross sectional view of another exemplary implementation ofthe outer tubular layer of the sheath.

FIG. 6 is a magnified view of part of the outer tubular layer of FIG. 5,showing the cross section of longitudinal rods in greater detail.

FIG. 7 is a cross section of an exemplary implementation of the innertubular layer of the sheath.

FIG. 8 is a cross section of both the inner and outer tubular layers ofthe sheath. In this example, the inner tubular layer is in thecompressed condition.

FIG. 9 is a perspective view of the distal end of an implementation ofthe expandable sheath.

FIG. 10 is a side view of one implementation of the expandable sheath.

FIG. 11 is a perspective view of one embodiment of a flared distalportion of the sheath.

FIG. 12 shows a side view of the distal portion of a sheath folded in aheat-shrink tube.

FIG. 13 shows a longitudinal cross section of an embodiment of thedistal portion of the sheath including a radioopaque tubular layer.

FIG. 14 shows an example flared distal portion of a sheath in a foldedconfiguration.

FIG. 15 shows a cross section of a distal portion of a sheath in afolded configuration.

FIG. 16 shows a sheath during passage of an implant. The inner and outertubular layers are adhered together in a longitudinally extending strip.

FIG. 17 shows a cross section of an exemplary embodiment includinglongitudinal rods embedded in the outer tubular layer and protrudinginto the elastic lumen.

FIG. 18 shows a cross section of an exemplary embodiment includinglongitudinal rods embedded in the outer tubular layer and protrudinginto the elastic lumen and outward from the outer surface of the outertubular layer.

FIG. 19 shows a cross section of an exemplary embodiment includinglongitudinal rods embedded in the outer tubular layer, where some rodsprotrude into the elastic lumen and others protrude outward from theouter surface of the outer tubular layer.

FIG. 20 shows a cross section of an exemplary embodiment includinglongitudinal rods embedded in the outer tubular layer and the innertubular layer. The longitudinal rods embedded in the outer tubular layerprotrude into the elastic lumen and the longitudinal rods embedded inthe inner tubular layer protrude into the central lumen.

FIG. 21 shows a cross section of another exemplary embodiment includinglongitudinal rods embedded in the outer tubular layer and protrudinginto the elastic lumen.

FIG. 22 shows a side view of the sheath with an implant passingtherethrough.

FIG. 23 shows a flared implementation of a distal portion of the sheath,where the flared portion is folded into a compressed configuration.

FIG. 24 shows the distal portion of FIG. 23 with the flared portionunfolded and expanded.

FIG. 25 shows a cross section of the distal portion of FIG. 23, wherethe flared portion is folded into a compressed condition.

FIG. 26 shows a perspective view of an exemplary implementation of theexpandable sheath.

FIG. 27 shows a longitudinal cross section of the proximal region of theimplementation shown in FIG. 26.

FIG. 28 shows a longitudinal cross section of the distal region of theimplementation shown in FIG. 26.

FIG. 29 shows a cross section of the distal region of the implementationshown in FIG. 26.

FIGS. 30 through 38 show a method of assembling a stiffened and sealedtip for another embodiment of the expandable sheath.

DETAILED DESCRIPTION

The following description of certain examples of the inventive conceptsshould not be used to limit the scope of the claims. Other examples,features, aspects, embodiments, and advantages will become apparent tothose skilled in the art from the following description. As will berealized, the device and/or methods are capable of other different andobvious aspects, all without departing from the spirit of the inventiveconcepts. Accordingly, the drawings and descriptions should be regardedas illustrative in nature and not restrictive.

For purposes of this description, certain aspects, advantages, and novelfeatures of the embodiments of this disclosure are described herein. Thedescribed methods, systems, and apparatus should not be construed aslimiting in any way. Instead, the present disclosure is directed towardall novel and nonobvious features and aspects of the various disclosedembodiments, alone and in various combinations and sub-combinations withone another. The disclosed methods, systems, and apparatus are notlimited to any specific aspect, feature, or combination thereof, nor dothe disclosed methods, systems, and apparatus require that any one ormore specific advantages be present or problems be solved.

Features, integers, characteristics, compounds, chemical moieties, orgroups described in conjunction with a particular aspect, embodiment orexample of the invention are to be understood to be applicable to anyother aspect, embodiment or example described herein unless incompatibletherewith. All of the features disclosed in this specification(including any accompanying claims, abstract, and drawings), and/or allof the steps of any method or process so disclosed, may be combined inany combination, except combinations where at least some of suchfeatures and/or steps are mutually exclusive. The invention is notrestricted to the details of any foregoing embodiments. The inventionextends to any novel one, or any novel combination, of the featuresdisclosed in this specification (including any accompanying claims,abstract, and drawings), or to any novel one, or any novel combination,of the steps of any method or process so disclosed.

It should be appreciated that any patent, publication, or otherdisclosure material, in whole or in part, that is said to beincorporated by reference herein is incorporated herein only to theextent that the incorporated material does not conflict with existingdefinitions, statements, or other disclosure material set forth in thisdisclosure. As such, and to the extent necessary, the disclosure asexplicitly set forth herein supersedes any conflicting materialincorporated herein by reference. Any material, or portion thereof, thatis said to be incorporated by reference herein, but which conflicts withexisting definitions, statements, or other disclosure material set forthherein will only be incorporated to the extent that no conflict arisesbetween that incorporated material and the existing disclosure material.

As used in the specification and the appended claims, the singular forms“a,” “an” and “the” include plural referents unless the context clearlydictates otherwise. Ranges may be expressed herein as from “about” oneparticular value, and/or to “about” another particular value. When sucha range is expressed, another aspect includes from the one particularvalue and/or to the other particular value. Similarly, when values areexpressed as approximations, by use of the antecedent “about,” it willbe understood that the particular value forms another aspect. It will befurther understood that the endpoints of each of the ranges aresignificant both in relation to the other endpoint, and independently ofthe other endpoint.

“Optional” or “optionally” means that the subsequently described eventor circumstance may or may not occur, and that the description includesinstances where said event or circumstance occurs and instances where itdoes not.

Throughout the description and claims of this specification, the word“comprise” and variations of the word, such as “comprising” and“comprises,” means “including but not limited to,” and is not intendedto exclude, for example, other additives, components, integers or steps.“Exemplary” means “an example of” and is not intended to convey anindication of a preferred or ideal aspect. “Such as” is not used in arestrictive sense, but for explanatory purposes.

Disclosed embodiments of an expandable sheath can minimize trauma to thevessel by allowing for temporary expansion of a portion of theintroducer sheath to accommodate the delivery system, followed by areturn to the original diameter once the device passes through. Theexpandable sheath can include, for example, an integrally formed innertubular layer with thick and thin wall portions, wherein the thin wallportion can expand to an expanded lumen for passage of an implant andthen fold back onto itself under biasing of an outer elastic tubularlayer after departure of the implant. In another aspect, the expandablesheath can include one or more longitudinally oriented stiffeningelements (such as rods) that are coupled to the elastic outer layer toprovide stiffness for the expandable sheath. Some embodiments cancomprise a sheath with a smaller profile than the profiles of prior artintroducer sheaths. Furthermore, present embodiments can reduce thelength of time a procedure takes, as well as reduce the risk of alongitudinal or radial vessel tear, or plaque dislodgement because onlyone sheath is required, rather than several different sizes of sheaths.Embodiments of the present expandable sheath can avoid the need formultiple insertions for the dilation of the vessel.

Disclosed herein are elongate delivery sheaths that are particularlysuitable for delivery of implants in the form of implantable heartvalves, such as balloon-expandable implantable heart valves.Balloon-expandable implantable heart valves are well-known and will notbe described in detail here. An example of such an implantable heartvalve is described in U.S. Pat. No. 5,411,552, and also in U.S. PatentApplication Publication No. 2012/0123529, both of which are herebyincorporated by reference. The elongate delivery sheaths disclosedherein may also be used to deliver other types of implantable devices,such as self-expanding implantable heart valves, stents or filters. Theterm “implantable” as used herein is broadly defined to meananything—prosthetic or not—that is delivered to a site within a body. Adiagnostic device, for example, may be an implantable.

FIG. 1 illustrates an exemplary sheath 8 in use with a representativedelivery apparatus 10, for delivering an implant 12, or other type ofimplantable, to a patient. The apparatus 10 can include a steerableguide catheter 14 (also referred to as a flex catheter) and a ballooncatheter 16 extending through the guide catheter 14. The guide catheter14 and the balloon catheter 16 in the illustrated embodiment are adaptedto slide longitudinally relative to each other to facilitate deliveryand positioning of the implant 12 at an implantation site in a patient'sbody, as described in detail below. The sheath 8 is an elongate,expandable tube that can include a hemostasis valve at the opposite,proximal end of the sheath to stop blood leakage.

Generally, during use a distal end of the sheath 8 is passed through theskin of the patient and inserted into a vessel, such as thetrans-femoral vessel. The delivery apparatus 10 can be inserted into thesheath 8 through the hemostasis valve, and the implant 12 can then bedelivered and implanted within the patient.

As shown in FIG. 2, the sheath 8 includes a hub 20, a flared proximalend 22 and a distal tip 24. The hub 20 is constructed of a rigidcylindrical structure defining a hub lumen 21 and houses a hemostasisvalve 26 and may define a side port 28 and have a threaded distal end30. The flared proximal end 22 of the sheath 8 includes a threadedfemale connector 32 mounted on a tubular wall structure 34. The distaltip 24 of the sheath 8 is mounted over a distal end of the tubular wallstructure 34, as shown in FIG. 3. The tubular wall structure 34 definesa central lumen 38.

The hub 20 is attached to the flared proximal end 22 by twisting thethreaded distal male end 30 into correspondingly threaded femaleconnector 32. This places the hub lumen 21 in communication with thecentral lumen 38 of the tubular wall structure 34. The hemostasis valve26 mediates access by the delivery apparatus 10 to the hub lumen 21 andcentral lumen 38 and ultimate deployment of the implant 12 in apressurized (blood filled) environment. Side port 28 provides anadditional access for application of saline or other fluids.

The distal tip 24, meanwhile, provides some restraint to the otherwiseradially expandable tubular wall structure 34. The distal tip 24 alsohelps with advancement over an introducer by providing a taperedadvancement surface. Further the distal tip 24 improves the stiffness ofthe sheath 8 at its distal tip to guard against buckling or collapse ofthe tubular wall structure 34 during torque and advancement forces.

As shown in FIG. 3A, the tubular wall structure 34 includes an elasticouter tubular layer 40 and an inner tubular layer 42 and the distal tip24. The distal tip 24 generally has a tubular structure with a slightlytapering or frusto-conical distal end. The distal tip 24 includes anouter wall 44, an inner wall 46 and a retainer 48. The outer wall 44 hasan axial length longer than the inner wall 46. A proximal end of theouter wall 44 has a tubular shape with straight sides. The outer walltapers to a neck 52 at its distal free end and begins to flare slightlyto a cylindrical bulge 50 moving proximally from the distal free end.The neck 52 has a smaller diameter than the proximal tubular end of theouter wall 44. The proximal tubular end in turn has a smaller diameterthan the cylindrical bulge 50.

The inner wall 46 has a shorter axial length than the outer wall butalso has a cylindrical shape that tapers—although more gradually—towardits distal free end. An outer surface of the inner wall 46 and innersurface of the outer wall 44 define an annular space 54 which isconfigured to receive a distal free end of the elastic outer tubularlayer 40, as shown in FIG. 3A. The annular space 54 bulges some due toits position subjacent the cylindrical bulge 50 of the outer wall 44.This bulge facilitates insertion and capture of the elastic outertubular layer. The annular space 54 tapers to a point moving distally asthe surfaces of the outer wall 44 and inner wall 46 converge intobinding contact.

The retainer 48 is an additional arc-shaped wall that extends along aportion of the inner surface of the inner wall 46 and defines its owncrescent-shaped space 56, as shown in the cross section of FIG. 3B. Thecrescent-shaped space 56 is configured to receive a foldable thin wallportion of the inner tubular layer 42, as will be described in moredetail below. The retainer 48 has an arc size that corresponds with acircumferential arc-length of the folded over portion of the innertubular layer 42 when it is in its compressed or folded configuration.Advantageously, the distal tip 24 helps to increase the structuralrigidity of the distal end of the tubular wall structure 34, blocksblood flow between the layers and provides a smooth, tapered profile forpushing through tissue when advanced over a wire or dilator.

As shown in FIG. 4, the outer tubular layer 40 of one embodiment has acylindrical shape with a circular cross-section along its entire length.The outer tubular layer 40 defines an initial elastic lumen 58 extendingaxially through its cylindrical cross-section. The outer tubular layeris sized to accommodate the delivery passage of the patient and/or thesize of the implant 12 to be delivered. For example, the insidediameter, ID, of the layer 40 may be 0.185 inches and may have a wallthickness of 0.005+/−0.001 inches for delivery of a stent-mounted heartvalve through trans-femoral access. In one aspect, inner surface of theouter tubular layer 40 and/or outer surface of the inner tubular layer42 may be treated to have or have applied thereto a lubricious coatingto facilitate unfolding and folding of the inner tubular layer 42.

The elastic lumen 58 is referred to as “initial” to designate itspassive or as-formed diameter or cross-sectional dimension when notunder the influence of outside forces, such as the implant 12 passingtherethrough. It should be noted, however, that because the outertubular layer 40 is comprised in the illustrated embodiment by anelastic material it may not retain its shape under even light forcessuch as gravity. Also, the outer tubular layer 40 need not have acylindrical cross-section and instead could have oval, square or othercross-sections which generally can be configured to meet therequirements of the inner tubular layer 42 and/or expected shape of theimplant 12. Thus, the term “tube” or “tubular” as used herein is notmeant to limit shapes to circular cross-sections. Instead, tube ortubular can refer to any elongate structure with a closed-cross sectionand lumen extending axially therethrough. A tube may also have someselectively located slits or openings therein—although it still willprovide enough of a closed structure to contain other components withinits lumen(s).

The outer tubular layer 40, in one implementation, is constructed of arelatively elastic material that has enough flexibility to mediate theexpansion induced by passage of the implant 12 and expansion of theinner tubular layer 42 while at the same time having enough materialstiffness to urge the inner tubular layer back into an approximation ofthe initial diameter once the implant has passed. An exemplary materialincludes NEUSOFT. NEUSOFT is a translucent polyether urethane basedmaterial with good elasticity, vibration dampening, abrasion and tearresistance. The polyurethanes are chemically resistant to hydrolysis andsuitable for overmolding on polyolefins, ABS, PC, Pebax and nylon. Thepolyuerthane provides a good moisture and oxygen barrier as well as UVstability. One advantage of the outer tubular layer 40 is that itprovides a fluid barrier for the pressurized blood. Other materialshaving similar properties of elasticity may also be used for the elasticouter tubular layer 40.

FIG. 5 shows another implementation of the elastic outer tubular layer40 including a plurality of longitudinal rods 60. The longitudinal rods60 extend the length of the outer tubular layer 40 and protrude into theinitial elastic lumen 58. The longitudinal rods 60 are coupled to theouter tubular layer, such as by being co-extruded and/or embedded intothe elastic material of the outer tubular layer, as shown in FIG. 6.Advantageously, the longitudinal rods 60 are configured to provide abearing surface to facilitate relative movement of the inner tubularlayer 42 within the outer tubular layer 40. This is especially helpfulwhen the inner tubular layer 42 is unfolding and returning to itsoriginally folded shape.

The longitudinal rods 60 may be circumferentially spaced about theinside surface of the outer tubular layer 60. Although fifteenlongitudinal rods 60 are shown in the cross-section of FIG. 5, anynumber, including a single one, of longitudinal rods may be employed.Also, the longitudinal rods 60 need not extend the entire length of theouter tubular layer 60. They may instead be applied selectivelydepending upon the demands of the implant, application and othercircumstances. Longitudinal rods 60 may be selectively left out of anoverall spacing pattern, such as in FIG. 5 where approximately 90degrees of the inside surface of the outer tubular layer 40 is left asan unadorned surface.

As shown in FIG. 6, the longitudinal rods may have a circularcross-section so as to present a curved bearing surface into the elasticlumen 58. Although diameters for the longitudinal rods 60 may vary, inone embodiment they are 0.004 inches in diameter. The outermost part ofthe longitudinal rod is positioned about 0.006 inches from the outsidesurface of the outer tubular layer 40. In this manner, the inner edgesurface of the longitudinal rods 60 spaces the inner tubular layer 42from the surface of the outer tubular layer 40, thus reducing frictionor the tendency to stick and impede relative movement. In otherembodiments, the longitudinal rods can have other shapes, and the shapesmay change within a single rod along the longitudinal direction. As alsoshown in FIG. 6, the material of the outer tubular layer 40 extends upin a slope past the midpoint of the cross-section of the longitudinalrods 60 for extra stability.

As shown in FIG. 7, the inner tubular layer 42 has a thick wall portion62 integrally extruded with a thin wall portion 64. The thick wallportion 62 is approximately 0.011+/−0.001 inches and the thin wallportion 66 is approximately 0.0065+/−0.0010 inches. The inner tubularlayer 42 is preferably constructed of a relatively (compared to theouter tubular layer 40) stiff material such as a stiff polymer like highdensity polyethylene (HDPE) or an equivalent polymer. Integralconstruction, such as integral extrusion, of the wall portionsadvantageously avoids the leakage of prior-art sheaths that use a splitin the sheath to promote expandability. Prior-art C-sheaths tend to leakclose to the proximal end at the manifold where the sheath is stretchedthe most. Also, integral construction improves the ability to torque thesheath 8.

The thick wall portion 62, in the illustrated embodiment of FIG. 7, hasa C-shaped cross section with a first longitudinally extending end 66and a second longitudinally extending end 68. The ends are where thethickness of the thick wall portion 62 starts to narrow to thin portion64 on the cross-section. That transition extends longitudinally in thedirection of the axis of the sheath 8, such that the thick wall portion62 forms an elongate C-shaped channel.

From those ends 66, 68 of the thick wall portion 62 extends the thinwall portion 64 and together they define a tubular shape. Extendinglongitudinally in that tubular shape is the central lumen 38. FIG. 7, inparticular, shows the central lumen 38 in its expanded diameter which islarger than the initial diameter of the elastic outer tubular layer 40.For example, the inner tubular layer 42 has a central lumen 38 that isabout 0.300+/−0.004 inches. The outer tubular layer 40 has an initialelastic lumen 58 of about 0.185 inches.

FIGS. 8 and 9 show the inner tubular layer 42 in its compressed orfolded condition, folded up and fit into the initial elastic lumen 58 ofthe outer tubular layer. In the compressed condition, the elastic outertubular layer 40 urges the first longitudinally extending end 66 underthe second longitudinally extending end 68 of the inner tubular layer42. This positions the thin wall portion 64 between the first and secondlongitudinally extending ends 66, 68.

FIG. 10 shows a side view of an implant moving through sheath 8. Duringpassage of an implant through the central lumen 38, the tubular wallstructure 34 takes on a locally expanded condition corresponding to thelength and geometry of the implant 12. In the expanded condition, thefirst and second longitudinally extending ends 66, 68 radially expandapart, against the urging of the elastic outer tubular layer 40 bypassage of the implant 12, into a non-overlapping condition with thethin wall portion 64 extending therebetween to form the expanded lumen,as in FIG. 7. After passage of the implant 12, the inner tubular layer42 is urged by the outer elastic tubular layer 40 into the compressedcondition shown in FIGS. 8 and 9. With this configuration, a 14 Frenchsheath 8 allows passage of a 29 mm transcatheter heart valve, such asthe Sapien XT and Sapien 3 transcatheter heart valves available fromEdwards Lifesciences.

As another option, the inner tubular layer 42 may be adhered along oneor more longitudinally extending portions of the outer tubular layer 40.Adhesion may be by heat fusion between the two layers or adhesivebonding, for example. As shown in FIG. 9, the longitudinally extendingportion can be a strip 70 where the outer surface of the inner tubularlayer 42 is bonded or otherwise adhered to the inner surface of theouter tubular layer 40. Preferably, the strip 70 is positioned oppositethe thin wall portion 64 to be away from, and not affect, the fold ofthe inner tubular layer 42. Inhibiting folding would also raise the pushforce for passage of the implant 12. Another implementation may includea second thin bonding strip 70 or line. Although the thickness of thestrip 70 can vary, preferably it is relatively narrow to reduce itsinhibition of expansion of the two layers and any increases in pushingforce. Use of a narrow bonding line between the layers 40, 42 preventsfree rotation of the layers with respect to each other while minimizingthe effect on push force.

In another embodiment, as shown in FIGS. 11-15, the distal tip 24 ofsheath tubular wall structure 34 can be a sealed tip to mitigate bloodintrusion and/or facilitate expansion at the distal end of travel of theimplant 12. In one aspect, a distal portion of the tubular wallstructure 34 may be reflowed to adhere the inner and outer layers 40,42, as shown in FIG. 11. In particular, the two layers 40, 42 are urgedinto their fully expanded (unfolded condition) and then reflowed to bindthe outer surface of the inner tubular layer 42 to the inner surface ofthe outer tubular layer 40. Then, the reflowed portion is returned tothe compressed or folded configuration and compressed under a heatshrink layer 74 to set the fold. The heat shrink layer 74 is thenremoved. Thus, when the distal end of the wall structure 34 folds, theouter tubular layer 40 is also folded, as shown in FIGS. 14 and 15.Sealing the tip stops blood from getting between the two layers 40, 42at the distal end of the sheath 8 while maintaining the highlyexpandable performance of the tubular wall structure 34.

The reflowed outer tubular layer 40 may have added thereto a radiopaquering 72. The radiopaque ring 72 can be adhered outside (such as by heatshrinking) and around the reflowed, folded distal portion of the outertubular layer 40. The ring 72 may be applied (such as by reflowing)outside the outer tubular layer 40 (FIG. 13) or inside the outer tubularlayer 40 (FIG. 12). The ring 72 is preferably constructed of a highlyelastic polymer to allow expansion and facilitate urging the tip backinto a folded configuration.

Advantageously, the outer tubular layer 40 and inner tubular layer 42are both seamless, which stops blood leakage into the sheath 8. Theseamless construction of the inner tubular layer 42 eliminates the endsof a conventional C-sheath. Elimination of the cut in the C-sheath byaddition of thin portion 64 improves torque performance. Also, bothlayers are easily manufactured by an extrusion process. The elasticouter tubular layer 40 has an elastic material that is similar to or thesame as most soft tips, making their attachment much easier.

As shown in FIGS. 17-20, other embodiments of the sheath 8 may include aconventional C-shaped inner tubular layer 42 surrounded by an elasticouter tubular layer 40 employing longitudinal rods 60. (FIGS. 17-20 mayalso use other types of inner tubular layer 42, such as the integrallyformed ones disclosed herein.) FIG. 17 shows use of seven longitudinalrods equally spaced from each other about the interior surface of theouter tubular layer 40 with the exception that a rod is missing from aportion adjacent a split in the inner tubular layer 42. This gapfacilitates distraction and return of the free edges of the C-shapedinner tubular layer 42. FIG. 18 shows a similar arrangement but with theeighth longitudinal rod 60 present. But the rod is somewhat offset fromthe location of the free edges of the inner tubular layer 42.Furthermore, the rods of FIG. 18 protrude outward from the outer surfaceof the outer tubular layer 40 to lower friction between the sheath and,for example, a body lumen or an additional outer delivery sheath.

FIG. 19 shows another embodiment wherein rods are embedded in the outertubular layer 40 and extend from the inside and outside surfaces thereofin alternation. This can lower friction from advancement of the sheath 8wherein, for example, the outer surface of the layer 40 touches a bodylumen or additional outer delivery sheath. FIG. 20 shows anotherembodiment wherein the inner tubular layer 42 also includes a pluralityof longitudinal rods 60 that facilitate, for example, easy passage ofthe implant 12.

The outer tubular layer 40 in the configurations of FIGS. 17-20 stillcan have a highly elastic, thin structure to fit over the conventionalC-sheath inner tubular layer 42. As the outer tubular layer 40 is notadhered to the inner tubular layer 42, there is free movement betweenthe sleeve and the delivery catheter 10. The outer tubular layer 40 isalso seamless to guard against blood leakage. The sheath 8 is stretchedevenly along all segments in a radial direction—reducing the risk oftearing or fracture. And, the elastic outer tubular layer 40 will urgethe C-shaped sheath back into the reduced profile configuration. Duringconstruction, the inner layer 42 is easily fitted inside the outer layer40 without flattening or heat wrapping. Implementations may include alarge number of longitudinal rods 60—even 100 or more depending upontheir cross-sectional size. The longitudinal rods 60 may includemicrostructure patterns that further reduce friction.

FIGS. 21 and 22 show yet another embodiment of the sheath 8 including asegmented outer tubular layer 40 having longitudinal rods 60 that may beemployed with or without an inner tubular layer 42. As shown in FIG. 21,the outer tubular layer 40 has elongate cuts or grooves that formelongate segments 76 extending axially along inner surface. Formed ormounted along the grooves are the longitudinal rods 60. The longitudinalrods 60 are shown in FIG. 21 to have curved or arc-shaped top surfacesthat reduce friction for passing implants 12. The longitudinal rods 60are comprised of relatively high stiffness materials such as HDPE,fluropolymer and PTFE. The outer tubular layer 40 can be constructed ofhighly elastic materials with a low tensile set (TPE, SBR, silicone,etc.) to facilitate recovery after expansion. When used without an innertubular layer 42, the outer tubular layer 40 can have additionallylowered expansion force—especially because the higher strength material(the rods) are not connected in the radial direction. Other variationsmay include changing the number and shape of the rods 60, incorporationof a tie layer or undercut/bard to strengthen the connection of the rodsto the outer layer 40 and adding sections of stiff material to theoutside of the outer layer for improved stiffness and pushability. Aslip additive may be applied to the surfaces to increase lubricity. FIG.22 shows the bulge in the sheath 8 as the implant 12 passestherethrough.

FIGS. 23-25 show another embodiment wherein a distal end of the tubularwall structure 34 can have a flared portion 78. The flared shape of theflared portion 78 helps to reduce snags or interference during retrievalexperienced with conventional sheaths during retrieval of medicaldevices. The flared portion 78 is folded or wrapped around the tapereddistal end of an introducer 80 to maintain a low profile foradvancement, as shown in FIGS. 23 and 25. The number and size of thefolds may vary depending upon the size and material type of the tubularwall structure 34. For example, FIG. 25 shows three folds in across-sectional view. After the distal end of the sheath 8 is inposition, the introducer 80 is removed. Then, the sheath 8 is ready toreceive the delivery catheter 10 and implant 12. When the implant 12reaches the flared portion 78 the folds then break and expand into theflared configuration, as shown in FIG. 24. The flared portion 78 remainsin this flared configuration for possible retrieval of the implant 12.

FIGS. 26-29 show another embodiment of the sheath 8. The sheath 8includes the tubular wall structure 34 that extends from the proximalend (as shown in cross-section in FIG. 27) to the distal end (FIGS. 28and 29). Generally, the tubular wall structure 34 includes inner tubularlayer 42, inner tip layer 81, strain relief tubular layer 82, outer tiplayer 84 and the elastic outer tubular layer 40.

As can be seen the tubular wall structure 34 has different layersdepending up on the axial position. The wall structure 34 includes astrain relief tubular layer 82 that terminates about ⅔ of the way fromthe proximal end, as shown in FIG. 27. The strain relief layer 82 ispreferable comprised of a relatively stiff material, such as HDPE, thatcan withstand the strains of the proximal end of the sheath 8 where itis joined to the hub and 20 and other components for accepting initialinsertion of the delivery apparatus 10. It terminates short of thedistal end of the sheath 8 to facilitate a greater flexibility and lowerprofile of the distal end of the sheath 8.

Extending past the strain relief tubular layer 82 the tubular wallstructure 34 drops down to two layers, the inner tubular layer 42 andelastic outer tubular layer 40. On the proximal-most end of the portionof the sheath 8 shown in FIG. 27, the inner tubular layer splits (incross-section) into its thick wall portion 62 and thin wall portion 64in the folded over configuration.

At the distal end, as shown in FIGS. 28 and 29, the sheath 8 includestip structure (including inner tip layer 81 an outer tip layer 84)configured to taper the wall structure 34 and seal the free end of thelayers against blood or fluid invasion. Generally, these componentsbuild up the diameter of a length of the wall structure 34 with someadditional layers including stiffening layers, and then tapers out andover the distal free end of the inner tubular layer 42.

The inner tubular layer 42 is similar to that described above. Itincludes the thin wall portion 64 that is configured to fold over intothe folded configuration back onto the thick wall portion 62. Also, theelastic outer tubular layer 40 restrains the inner tubular layer 42against expansion. But, the elasticity of the outer tubular layer 40 canalso be overcome to allow the inner tubular layer to at least partiallyunfold into a wider central lumen 38 for passage of the implant 12 orother device.

As shown in FIG. 28, the inner tip layer 81 extends only a short axiallength. In particular, the inner tip layer 81 extends around and pastthe distal-most end of the foldable inner tubular layer 42, taperinginto smaller diameter free end after extending distally past the freeend of the foldable inner tubular layer. As shown in the cross-sectionorthogonal to the long axis of the sheath 8 of FIG. 29, the inner tiplayer 81 has a C-shaped cross-section. (The top of the C-shape isenlarged somewhat to account for the overlapping layers of the wallstructure 34—so that the free longitudinal edges are radially spacedapart to form a gap.) The C-shaped cross-section allows the freelongitudinal edges of the inner tip layer 81 to spread apart duringunfolding of the inner tubular layer 42. Advantageously, the innertubular layer 42 has a relatively stiff material construction smoothing,stiffening and tapering the distal end of the sheath 8 as well asproviding some protection for the free end of the inner tubular layer42. The inner tip layer 81 also advantageously extends over the distalend of the inner tubular layer 42, thereby sealing the thick and thinwall portions 62, 64 against blood and fluid invasion.

The outer tip layer 84 extends over and is adhered to the inner tiplayer 81 and a distal portion of the inner tubular layer 42. The outertip layer 84 covers the proximal edge of the inner tip layer 81, sealingit against the inner tubular layer 42. The outer tip layer 84 is of arelatively bendable material and, where it is directly adhered to thethin wall portion 64, can be folded over onto itself as shown in FIG.28. Advantageously, then, the outer tip layer 84 tracks the unfolding ofthe thick and thin wall portions 62, 64 to continue to seal the innertip 81 to the inner tubular layer 42. Notably, as the outer tip layer 84unfolds the free longitudinal edges of the C-shaped inner tip layer 81can come apart for coordinated lumen expansion of the sheath 8. But,also, at the same time the stiffness of the inner tip layer 81 and extrareinforcement of the outer tip layer 84 help to maintain tip stiffnessand stability.

The elastic outer tubular layer 40 extends all the way to the distal endof the sheath 8, including over the distal end of the outer tip layer84. In addition, the inside of the elastic outer tubular layer includesrods 60 extending axially and reducing unfolding resistance by loweringsurface area and increasing lubricity.

The sheath 8 may also include a radiopaque marker band or layer portion86 that provides an orientation and depth indication under radioscopyduring implantation or other medical procedures.

FIGS. 30 through 38 show a method of assembling a stiffened and sealedtip for another embodiment of the sheath 8. FIGS. 30-38 show varyingviews of the same sheath 8 as it undergoes the method of assembly. FIGS.30 and 31 show the inner tubular layer 42 (to the right) in the unfoldedconfiguration. An additional tubular layer 92 (such as a strain reliefor elastic layer) (to the left) extends over the inner tubular layer 42but stops short of the free end of the inner tubular layer. FIG. 31shows a portion of the radiopaque marker 86 attached to the innertubular layer 42.

FIG. 32 shows the inner tubular layer 42 with a window or v-shaped notch90 cut into its free end to allow for tip expansion. The v-shaped notch90 also facilitates retrieval of an implant. FIG. 32 also shows theC-shaped inner tip layer 81 extended around an outside of the innertubular layer. FIG. 33 shows a second notch 90 on the opposite side ofthe inner tubular layer 42. Also in FIG. 33, the distal tip of thepartially constructed sheath 8 is extended over a mandrel 94 tofacilitate folding and attachment of other layers.

FIG. 34 shows formation of a proximal hemostasis seal by application ofa proximal sealing layer 96 that extends around a distal free end of theadditional tubular layer 92 and over and past the distal end of theemerging inner tubular layer 42. In the embodiment shown in FIG. 34, theproximal sealing layer 96 is transparent such that the v-shaped notch 90is visible from underneath the sealing layer 96. A proximal section 98of the sealing layer 96 is heat treated to seal the transition betweenthe additional tubular layer 92 and the inner tubular layer 42, which insome embodiments can give proximal section 98 a glossier appearance thanthe remainder of sealing layer 96. The proximal section 98 blocks bloodand other fluids from entering between the two layers 42, 92.

FIG. 35 shows the layers 42, 92 and 96 being folded over ontothemselves. FIG. 36 shows the elastic outer tubular layer 40 or jacketwith rods 60 being unrolled over the now folded layers 42, 92 and 96.FIG. 37 shows the outer tubular layer 40 itself slightly folded at thedistal end and having applied thereover a distal sealing layer 100. Theexcess of the free end of the proximal sealing layer 96 extending pastthe distal sealing layer 100 is cut away. The distal sealing layeradvantageously urges the distal free end of the layers 40, 42 and 96into a tapered configuration and provides a rounded distal end for thetubular wall structure 34 that facilitates insertion and advancementover the guidewire.

In view of the many possible embodiments to which the principles of thedisclosed invention can be applied, it should be recognized that theillustrated embodiments are only preferred examples of the invention andshould not be taken as limiting the scope of the invention. Rather, thescope of the invention is defined by the following claims. We thereforeclaim as our invention all that comes within the scope and spirit ofthese claims.

What is claimed is:
 1. A method of manufacturing an expandable sheath, the method comprising: forming multiple longitudinally extending folded portions spaced in a circumferential direction around an inner member, each of the folded portions defined by an overlapping portion bounded between two longitudinally-extending fold edges; positioning at least two reinforcing members radially outward of the inner member such that each of the reinforcing members is generally equally spaced from a longitudinal axis of the inner member when the sheath is in a non-expanded configuration, at least one of the reinforcing members is spaced in a circumferential direction from the fold edges of each of the longitudinally extending folded portions, each of the at least two reinforcing members in the form of rods that extend longitudinally along a length of the sheath; positioning an outer member over the at least two reinforcing members and around the inner member; binding the outer member to the at least two reinforcing members; and cutting at least one notch in a distal end of the inner member.
 2. The method of claim 1, wherein forming the longitudinally extending folded portions comprises overlapping a longitudinal section of the inner member along an outer surface of the inner member.
 3. The method of claim 2, wherein overlapping a longitudinal section comprises pinching a longitudinal section of the inner member radially outward from the longitudinal axis of the inner member, then folding the longitudinal section such that an inner surface of the longitudinal section contacts the outer surface of the inner member.
 4. The method of claim 1, wherein forming the longitudinally extending folded portions comprises overlapping a longitudinal section of the inner member along an inner surface of the inner member.
 5. The method of claim 4, wherein overlapping the longitudinal section comprises pinching the longitudinal section of the inner member into a lumen of the inner member, then folding the longitudinal section such that an inner surface of the longitudinal section contacts the inner surface of the inner member.
 6. The method of claim 1, wherein forming the longitudinally extending folded portions comprises arranging two or more longitudinally extending segments of the inner member into an overlapping configuration to form the folded portions.
 7. The method of claim 6, wherein arranging two or more longitudinally extending segments of the inner member into an overlapping configuration to form the longitudinally extending folded portions further comprises wrapping the folded portions along an inner or outer surface of the inner member.
 8. The method of claim 6, wherein arranging two or more longitudinally extending segments of the inner member into an overlapping configuration to form the longitudinally extending folded portions comprises pinching first and second longitudinal segments of the inner member, then overlapping the pinched longitudinal segments with an inner surface of the inner member.
 9. The method of claim 6, wherein arranging two or more longitudinally extending segments of the inner member into an overlapping configuration to form the longitudinally extending folded portions comprises pinching first and second longitudinal segments of the inner member, then overlapping the pinched longitudinal segments with an outer surface of the inner member.
 10. The method of claim 1, further comprising spacing the longitudinally extending folded portions equally in the circumferential direction around the inner member.
 11. The method of claim 1, wherein each of the longitudinally extending folded portions is circumferentially bounded by two radially outwardly positioned reinforcing members.
 12. The method of claim 2, wherein positioning at least two reinforcing members comprises orienting the at least two reinforcing members generally parallel to each other and to a central longitudinal axis of the sheath, wherein a majority of the overlapping section of the inner member is provided between the at least two reinforcing members.
 13. The method of claim 1, wherein binding the outer member over the at least two reinforcing members comprises heating the outer member and the reinforcing members.
 14. The method of claim 13, wherein heating the outer member and the reinforcing members causes the reinforcing members to become embedded within a wall of the outer member.
 15. The method of claim 1, wherein cutting at least one notch comprises cutting the notch in a v-shape.
 16. The method of claim 1, further comprising applying a lubricious coating to an inner surface of the outer member.
 17. The method of claim 1, further comprising attaching the expandable sheath to a proximal hub.
 18. A method of manufacturing an expandable sheath, the method comprising: forming a longitudinally extending folded portion on an inner member, the longitudinally extending folded portion comprising a portion of the inner member circumferentially overlapping an other portion of the inner member and bounded between two fold edges; positioning at least two reinforcing members radially outward of the inner member such that they extend longitudinally along a length of the sheath and such that they are each equally spaced from a longitudinal axis of the inner member, at least one of the at least two reinforcing members is spaced in a circumferential direction from the fold edges of each longitudinally extending folded portion, each of the at least two reinforcing members in the form of rods that extend longitudinally along a length of the sheath; positioning an outer member over the at least two reinforcing members and around the inner member; heating the outer member and the reinforcing members to cause the reinforcing members to become embedded within a wall of the outer member; and cutting at least one notch in a distal end of the inner member. 